The field of this invention is closed-loop controllers, particularly for control loops to maintain, at least part of the time, a desired acceleration for a motor or other actuator.
Prior art motion controller typically monitor a position and respond with changes in a drive signal to maintain a desired position, which may be relatively static or dynamic. Other prior art controllers monitor a velocity and respond with changes to a drive signal to maintain a desired velocity, typically static, although sometimes dynamic.
A common feedback method is PID, or proportional-integration-differential, in which an error signal, and integrated error signal and a differentiated control signal are each is multiplied by three respective values and then summed to provide an updated drive signal.
Such prior art methods and devices, whether continuous, such as an analog system or discreet, such as a digital system, suffer from numerous weaknesses including: poor response to varying desired position or velocity; instability, poor response to varying loop gain; poor response in non-linear systems, poor response in non-symmetric systems, and an inability to adapt constants used in PID terms to actual or dynamically changing system characteristics.
Prior art systems for stepper motors are typically open loop, using the steps of the stepper motor to achieve a desired position, include micro-step and sinusoidal drive. Such systems suffer from noise, vibration, and non-linear motion. Such prior art systems are also unresponsive to non-linear motor performance between steps and changing system characteristics, such as varying or oscillating loads.